The present invention relates in general to apparatus for laser skin treatment, such as depilation. The invention relates in particular to an automatic repeat firing system for laser skin treatment apparatus which, in a single firing, can treat only a relatively small sub-area of an area of skin to be treated.
In laser dermatological treatment operations such as depilation, an area of skin to be treated may often be much greater than the area which can be treated by a single firing of laser apparatus. Typical apparatus for laser treatment includes a handpiece for delivering laser radiation from a laser to skin being treated. The laser may be remote from the handpiece with the laser radiation being delivered to the handpiece via an optical fiber or articulated arm. Alternatively, the laser radiation may be provided by a diode-laser array incorporated in the handpiece. A handpiece is often furnished with a cooled window which is placed in contact with the skin, laser radiation being delivered to the skin through the cooled window.
Treatment of a large area of skin is typically accomplished by an operator manually firing the laser apparatus, with the handpiece located in one position on the area of skin being treated, then moving the handpiece to another position in the treatment area and manually firing the laser apparatus again. One disadvantage of this method is that it can be difficult to precisely and contiguously locate treated sub-areas of the total area being treated such that no sub-area is left untreated and no overlapping of treated sub-areas occurs. Another disadvantage of this method is that time taken to relocate the handpiece from a treated sub-area to an adjacent untreated sub-area can prolong the treatment operation. This, in turn, can lead to an increased cost of the operation. The apparatus and method of the present invention is intended to overcome these disadvantages.
The present invention is directed to a method of treating an area of skin with a laser by delivering a series of laser-radiation pulses to the skin. Each of the laser pulses treats a sub-area of the area to be treated.
In one aspect of the present invention, a laser is provided which, on being fired, generates a pulse of laser-radiation. A handpiece is provided and arranged for delivering a pulse of laser-radiation from the laser to the skin being treated.
While the handpiece is being moved over the skin being treated, the location of the handpiece in the area of skin being treated is electronically determined, and the laser is automatically fired when the electronically determined location corresponds to a sub-area to be treated.
The terminology xe2x80x9cautomatically firedxe2x80x9d here means that as the firing of the laser is electronically triggered by the electronic position determination without operator intervention other than moving of the handpiece. The terminology xe2x80x9claserxe2x80x9d means a laser resonator including a gain medium (which may be a diode-laser or array of same) and those electrical and electronic circuits needed to power the laser and to switch or modulate the laser to provide the laser-radiation pulses.
In one embodiment of the present invention the location determining step includes providing a plurality of regularly spaced indicia on or adjacent the area of skin being treated. At least one sensor is provided on the handpiece and arranged to detect passage of the handpiece by one or more of the indicia as the handpiece is moved over the skin being treated. The automatic firing is triggered by the passage of the handpiece by one or more of the indicia. The indicia may be graphic indicia, magnetic indicia, or mechanical indicia.
In one example of this preferred embodiment of the present invention, the indicia are graphic (optically detectable) indicia. The sensor includes a light-source arranged to direct light onto the skin being treated such that the thus directed light is scattered by the skin being treated. The sensor includes one or more light detectors arranged to detect the light scattered by the skin. The graphic indicia are equally-spaced parallel lines drawn on the area of skin being treated in a medium which is opaque to the wavelength of light emitted by the light-source and transparent to the wavelength of said pulse of laser radiation. Passage of the handpiece by any one of the indicia (crossing any one of the lines) results in a reduction in the scattered light detected by the detector. The reduction in scattered light indicating that one of said indicia has been passed, i.e., a line has been crossed.
In another embodiment of the present invention the location determining step comprises providing a roller on the handpiece, the roller being-arranged to contact the skin being treated and rotate in response to the handpiece being moved over the skin being treated. The roller has a plurality of regularly spaced indicia thereon. At least one sensor is provided on the handpiece. The sensor is arranged to detect passage by the sensor of one or more of the indicia as the roller rotates. The automatic firing is triggered by the passage by the sensor of one or more of the indicia.
The indicia on the roller may be radially extending lines on a side of the roller or longitudinally extending lines on a cylindrical surface of the roller. The indicia in either case may be graphic (optically detectable) indicia or magnetic (magnetically detectable) indicia. In one variation of this embodiment, indicia can be omitted from the roller and the roller axially connected to a shaft encoder, the shaft encoder providing signals used for the electronic position determination.
In yet another embodiment of the present invention, the location determining step comprises providing a screen adjacent the skin being treated. A transponder is provided on the handpiece. The transponder is arranged to emit a regular train of signal-pulses toward the screen such that the signal-pulses are incident thereon and a return-pulse corresponding to each of the incident signal-pulses returns to the handpiece. A receiver is provided on the handpiece for receiving the return pulses. An elapsed time between emitting a signal-pulse and receiving a corresponding return-pulse is determined. The elapsed time is representative of the location of the handpiece.
The signal-pulses are preferably ultrasonic pulses. However, the use of other forms of signal pulses is possible, for example optical pulses or radar pulses.
In still another embodiment of the present invention the location determining step also includes providing a transponder on the handpiece. The transponder is arranged to emit a regular train of signal-pulses each thereof in diverging beam. At least two spaced-apart receivers are provided. The receivers are located in a position remote from the handpiece, within the divergence of the beam, for receiving said signal pulses. Based on the spacing of the receivers and an arrival time of the signal pulses at the receivers, the location of the handpiece is determined in at least length and width dimensions of the area of skin to be treated. For an area of skin to be treated which is contoured, three spaced-apart receivers may be provided, and the location of said handpiece in the area of skin to be treated determined in length width and height dimensions.
In another aspect of the present invention, the handpiece may be equipped with a skin contact-sensor for determining whether or not the handpiece is in contact with skin being treated. This is useful in laser skin treatments wherein laser radiation is delivered to the skin via a lens or transparent body (applicator) incorporated in the handpiece and in contact with the skin for promoting efficient coupling of laser radiation into dermal layers.
In one preferred embodiment of skin-contact sensing in accordance with the present invention, a light-source is provided having an exit-aperture thereof on the handpiece. The exit-aperture is configured to be in contact with the skin being treated when the applicator is in contact with the skin being treated. Light from said light-source is delivered via said exit-aperture thereof such that, when the applicator is in contact with the skin, light delivered via the said exit-aperture is transported laterally through the skin via volume scattering of the light. A detector is provided having a receiving-aperture on the handpiece proximate the light-source exit-aperture. The output of the detector is monitored. The monitored detector-output is interpreted as an indication that the applicator of the handpiece has made or lost contact with the skin being treated.
The above-described skin contacting method is not limited to a handpiece delivering laser-radiation for skin treatment but is applicable to handpiece delivering electromagnetic radiation (for skin treatment) from an incoherent source such as a flashlamp. An above-described sensor for detecting graphic indicia may be configured to additionally function as a skin sensor for implementing the above-described skin-contact sensing method.
Preferred embodiments of the present invention are described in detail hereinbelow with reference to a laser hair removal apparatus using an array of diode-lasers. Automatic firing arrangements in accordance with the present invention are neither limited to apparatus including diode-lasers, nor limited to hair removal apparatus. Those skilled in the art will recognize that automatic firing principles of the present invention are applicable to laser apparatus including other laser types, for example, solid-state lasers, to apparatus wherein treatment light is provided by an incoherent source of electromagnetic radiation such as a flashlamp, and to other laser skin treatments, for example, treatment of vascular lesions such as xe2x80x9cport winexe2x80x9d stains.